Compunction, n.
Etymology: [OF. compunction, F. componction, L. compunctio, fr. compungere, compunctum, to prick; com- + pungere to prick, sting. See Pungent.]
1. A pricking; stimulation. [Obs.] That acid piecering spirit which, with such activity and compunction, invadeth the brains and nostrils. Sir T. Browne.
2. A picking of heart; poignant grief proceeding from a sense of guilt or consciousness of causing pain; the sting of conscience. He acknowledged his disloyalty to the king, with expressions of great compunction. Clarendon.
Syn. -- Compunction, Remorse, Contrition. Remorse is anguish of soul under a sense of guilt or consciousness of having offened God or brought evil upon one's self or others. Compunction is the pain occasioned by a wounded and awakened conscience. Neither of them implies true contrition, which denotes self-condemnation, humiliation, and repentance. We speak of the gnawings of remorse; of compunction for a specific act of transgression; of deep contrition in view of our past lives. See Regret.
Shades of meaning
Fernald has no entry of its own for compunction; he lists it under repentance.
Where he writes about it:
Compunction is a momentary sting of conscience, in view either of a past or of a contemplated act. — from repentance